Method of and apparatus for testing the elastic properties of metals



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C. W. ROBBINS METHOD 0F AND APPARATUS FOR TESTING THE ELASTIC PROPERTIES OF METALS` Filed June l2, 1920 2 Sheets-Sheet 1720er? or Chdres Wffoms LaGrange,

Patented' Feb. 23, 1926,.

{UNI-TED STATES PATENT oFFI CHARLES .W. ROBBINS,

. OF LAGRANGE, ILLINOIS, .ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

METHOD OF AND APPARATUS FOR TESTING THE ELASTIC PROPERTIES OF METALS.

Application mea .Tune 12, 1920. serial 110,388,454.

To all whom t may concer-n.'

Be it known that I, CHARLES W. ROBBINS, a citizen of the United States, f'residng at in the' county of Cook and State of Illinois, have invented certain new and useful Improvements in a Method of and Apparatus for lTesting the Elastic Properties of Metals, of which the following is a full, clear, concise,l and exact description.

This invention relates to a method of and apparatus for testing the elastic properties of metals.

It is one of the' objects of this invention to provide a simple and accurate method for determining commercially the elastic properties of materials, and particularly of metals which may be used as contact springs and for like purposes in electrical apparatus.

In accordance with the general features of this invention, a method which, may be employed with good results for testing the elastic properties of materials consistsv in elongation under stress,

adapted to engage the free I which a quadrant rotatable with the deflecting a strip of the material of uuiform `cross section and given length out of a normal or zero plane with pressures of gradually increasing amounts, noting the defiection and permanent set for each pressure and continuing the readings beyond the pointy where. the sample first shows a permanent set. From the data thus obtained the results may be tabulated or curves drawn showing the modulus of elasticity,

elongation for the several amounts of stress applied.

The invention has as'another object the provision of a simple and convenient form of apparatus for applying the -pressure and taking the readings necessary for the determinations in the practice of the above method. vThe apparatus of this invention consists in general of a clampingmeans for A-holding one end of a sample strip to be tested, Iand a pressure applying means end of the strip, together .with a suitable scale Vfor measuring deflections, and armeans for determining 'the amount of pressure applied. A convenient vform for thel apparatus is` one in clamping means is divided into suitable scales for reading directly the deflection'of the strip under pressure, and a pressure applying means connected directly'wlth a balance beamwscale which" 1s `Weighted toV balance and permanent4 -member 6 connecting after each predetermined movement of the rotatable quadrant. 1

, Other features of -the invention relate to the details of construction of the apparatus for adjusting the balance beam scalelongitudinally to take care of thevarious lengths of test samples.

`In the drawings illustrating this invention:

Fig. 1 is a view in side elevation of a mechanism which may be used in the practice of the method of this invention and which embodies the novel features of the mechanism;

Fig. 2 is a View Fig. 1;

Fig. 3 is a fragmentary detail view. of a clamping mechanism and scale quadrant moved out of normal position;

Fig. 4 is a detail sectional View taken upon line 4-4 of Fig. l;

Fig. 5 is a fragmentary detail view on an enlarged scale of the pressure applying means showing its manner of engagement wicth a sample of the material to be tested, an

Fig. 6 is a fragmentary view on an enlarged scale of the means'for disengaging taken upon line 2 2 of l a quick movement thereof 1s desired.

Referring to Fig. 1 of the drawings, 5 designates a base or supporting vmember upon which is mounted the frame of a balance beam scale comprising a lower horizontal standards 7 and 8 and carrying a rack 9 a apted to be engaged by a pinion 10 controlled lby a hand wheel 11 for moving the scale longitudinally on the supporting basel 5 between guides. 12-12 and 13-13, one each of which -is shown on the drawing. At its upper end the standard 7 is provided with suitable supporting members,lv 14;-14 to receive knife edge supports 5 15-of a balance beam 16. At its opposite end the balance beam 16 extends through a slot 17 in the standard v8 which serves to limit its oscillating movement and is providednear its end with means for supporting a scale pan 18. A balance-adjusting micrometer is indicated at 19.41;!Af beam slide for balancing the beam to fractions of the pan weights is indicated at 20. On its the driving means from the quadrant when end adjacent the4 standard 7 the beam 16 ise-` provided with Aa projection 21 upon which is vertically extending rod 23 through the agency of which the amount of pressure applied to a test sampleA 25 for deiecting it through a` given angle or arc is determined, as will hereinafter more fully ap ear.

Extending upwardly from the ase member 5 is a supporting backing member -30 upon which is 'rotatably mounted a worm wheel 31, as more clearly shown in Figs. 2 and 4. Secured to rotate with the Worm wheel 31 is a quadrant 32 upon whichv is mounted'a scale bearing member 33 provided with a plurality of separately graduated lscale indications 34-34, each being adapted to provide for the deflection reading of different lengths of samples. Mount' ed upon the quadrant 32 is a vise or clamping member ,comprising jaws 35 and 36 and a clamping screw 37. The worm Wheel 31 is engaged by a worm 42 carried-upon the end of a shaft 43 Mwhich' is provided withl a hand wheel 44, the turning of which swings the quadrant 32 around the pivotal support of the wormwhe el 31. The outer end of the shaft 43 is supported in a horizontal position by means ofan adjustable supporting member 45 with the inner-end of the -shaft ball shaped, as indicated at 46, and supported in a suitable socket formed in a bearing 47. This construction permits the disengagement of the worm 42 from the wheel 31, thereby providing for moving the quadrant 32 more rapidly than it can be moved by turning the hand Wheel 44.

Inthe operation of this mechanism a test sample 25 of uniform cross section and given length is secured between the. jaws 35 and 36 ofi he vise/ or clamping member in such a position that a punched depression made in the sample will be engaged by the upper, end of the pressure rod 23 which is provided with a pointed portion 51 for this purpose.

/The parts will then be adjusted so that the test sample 25 will lie in a horizontal position without pressure upon it. The hand wheel 44 will then be turned to move the quadrant 32 through a slight angle and the balance beam scale will loe adjusted to balance and the amount of the pressure whichis being exerted between it andthe test sam le 25 will be noted. Also the amount of election of the test sample will be noted and the two readings tabulated. The sample will then be moved backward toits zero position which may be done` by disengaging the end of the rod 23 from it and the `amount of permanent set, if any, of the test sample 25 will be noted on its correspond.` ing scale. These readings will be `repeated with gradually increasing amounts of presj sure until the sam le hasbeen deiected coni dicated a permanent set.

siderably beyond t e point where it first in- For the best rerod 23 with the test sample should be opposite one of the scales at the zero position upon the quadrant 32 and the readings as the sample is deflected shouldpbe take-n at the point where the straight portion beyond the point. of engagement 'of the test ,sample and the pressure rod crosses the adjacent scale.

The length of the sample used should be proportional to the thickness and the force should be applied in a directie-n perpendicular to a line connecting the point at which the pressure'is applied and the edge of the clamp. The scales should be 'laid off in equal divisions of the circumference of a circle having a radiusequal to the length of vthe sample and the deflection read at the point in the corresponding scale Where the straight portion of the sample ator beyond the point of 4pressure crosses the graduated scale. The scale divisions will bein inches and fractions if Weights are in pounds and in centimeters if`weights are in kilograms. The length of the sample between points should be not more than 150 times the thickness. a

With this method and apparatus, if the above conditions vare observed, it is believed@v that the following formulae will give results that are approximately correct for deflections that do not exceed 45 or 50 degrees:

` E=Youngs Modulus lof Elasticity. 'y

W=Pressure. 05 IzMoment of inertia. S=Stress.

The maximum stress and elongation evi'- A115v dently .occur near the clamp.

Whatis claimed is: j

1. The method of testing the elastic properties of materials, which consists in fixing one end of a strip of material of uniform cross section and given length and delecting said strip out of a normal plane by gradually increasing known amounts in response to pressures applied at the free end,l noting the deflection pressures required and permanent set for each amount, and continuing the readings beyond thevpoint where the sample first begins to show'a permanent set.

2. The method of testing the elasticv properties of materials, which consists in clamping one end of a strip of uniform cross se'ction and given-length, deiecting the strip N by gradually increasing amounts by apply-I A ing pressures to the strip at its free,4 end and in a directiqn perpendicular toa line be- Y' tween the point oiJ application of the -pres-` sure and the edge of the lamp, noting the deliection, determining the.

yond'the point where the sample tirst begins to show a permanent set.

f 3. Iii an apparatus for testing the elastic rproperties of materials, means Vfor holding Y a strip of the material vto be tested, means for deflecting the material out of a normal plane, means associated with the holding i means for indicating directly the'amount of deflection, and meansassociated with the deilecting means for indicating directly the .amount of deflecting pressure,

. 4 IIL an apparatus for testmg theV elastic properties of materials, clamping'v means for holding astrip of material` to be tested,

means adaptedto engage a free end of the strip to causeit tovv be deflected out o@ a normal plane,means associated with the clamp'-l ing means for. indicating directly the amount of deiiection, and means associated with the r deiecting-means vfor 'indicating directlythe amount of vdeiectin'g pressure. v t 5. In anapparatus for testing the elastic 'properties of materials, a rotatable clamping f v means for holding ene end ofl a lstrip of material to be tested, a quadrant movable with said clamping means, and prvided 'with scales for designating the deection of theI Strip, means for engagin lthe free end' of -the strip to cause 1t to. v 4deiiected upon \4,.-mo'vement of the'clamping means, anda?- amount of pres-- sure and permanent set for each amount ofv l0 pressure, and continuing the readings be-4 `myname this balance beam scale membert4 for measuring the Adeiecting pressure. v

v6.11; an' a paratus for-testing the elastic properties o v-1I iaterials,- a rotatable clamping means for holdjngone end of 'a strip'of the material to be tested, means adapted' to engage'the free end of the stripftocause its deflection out of anormal plane, a balance beam scale-connected; withjsaid pressure means, and means lfor. shifting 'said' scale and 50 -pressure ,means longitudinally to compendeflection, means associated with the defiect- 60 v'iiig'means-for indicating directly the amount of delecting ressure, and means 'for compensating for? variations in the lengths of the strips to be tested. 8. In an apparatus forf'testing the elastic properties of materialsfmeans for holding a strip of the materialA to be tested, means or deiecting the material voluto a ynormal plane, means. associated with the4 holding means for indicating directlythe amount of deflection, means as'sociatedlwith the deiiect.-

. ing meansfforgindicatin'g directly the amount of deiectio'n, 'and meansj for.. adapting 'the indicating anddefiectingmeans to compenl.

sate for variationsl lin the lengths of ,the

stripstobetested.

' In witness whereof, I hereunto'subscribe A Y twenty-seventhv day of May GHABLESW. ROBBINSS l 

